The present invention is related to the field of semiconductor photolithography and, more particularly, to semiconductor optical projection systems.
In present semiconductor photolithography, optical projection systems are presently being used to print circuit patterns upon the surface of semiconductor wafers. Each circuit pattern is defined in a layer of a semiconductor device so that a sequence of these circuit patterns form the semiconductor device. As these devices become more compact and dense, the individual elements forming the semiconductor device become smaller and smaller. Feature sizes of many advanced integrated circuits today are smaller than 0.5 .mu.m.
These semiconductor photolithography projection systems have many refinements to enhance the printing capabilities of these systems. Among these refinements is the use of an off-axis mask for the illuminator lens of the projection system. The off-axis mask enhances the contrast of the pattern image which is projected onto a semiconductor wafer to create a circuit pattern on the wafer.
Nonetheless, there is still room for improvements in semiconductor photolithography projection systems. Unlike conventional semiconductor photolithography projection systems which take no advantage in emerging improvements in semiconductor technology, the present invention does.